Method and apparatus for producing light



A'pfil 25,-1933. E. F. NORTHRUP' METHOD AND APPARATUS FOR PRODUCINGLIGHT Filed June 11, 19:0

Patented A r. 25,1933

- UNITED STATES EDWIN FITCH NORTHRUP, OF PRINCETOIhl', NEW JERSEY METHODAND APPARATUS FOR PRODUGING l My invention relates to methods andapparatus for producing light.

lhe principal purpose of'my invention is to combine the advantages of anelectric incandescent lamp and of a glow lamp.

5 resonating the circuit to'secure maximum effectiveness and using highfrequency to reduce the capacity required for a given reactance.

quency current tor the purpose of producing lightunder conditions ofdesirable economy.

A further 'purpose is to obtain light on a commercial scale by thebombardment of an electron em ssion from a hot body against.

the molecules of gases and solids A further purpose is to lighta' lampfrom a circuit in which the conditions of series resonance obtain.

A further purpose is to produce light by maintaining a high potentialdifference between two or more hot bodies. Y

A further purpose is to connect a plurality of heated elements containedwithin a closed lamp to a source of alternating'eurrent.

A further purpose is to. maintain a potential difierence from analternating. source be-' tween a plurality of electrically heatedelements surrounded by .a'v'acuum or by a spe- 40 cial gaseousatmosphere. p I

A further purpose is to electrically heat a plurality of incandescentlamp filaments contained within a lamp, and to add to the lightgivingqualities of the filaments the glow produced by the luminescence ofgases contained in the lamp, due to electron emission from thefilaments.1

A further purpose is toconstruct combined incandescent "and glow lampswhich may be connected to a- .common current source in series or inparallel.

A further purpose is to utilize high fre- Figure 3 diagrammaticallyillustrates a 75 Application filed June 11, 1980. Serial No. 460,531.

Further purposes will appear in the specification and in the claims.

My invention relates both to the methods or processes involved and tostructure by whtich the methods or processes are carried ou Y I havepreferred to illustrate my invention by a'few embodiments only of thesame general form, selecting embodiments which are effective and fullyoperative but which have been selected primarily because of theirsuitabllity for illustration of the principles involved.

In the drawing like numerals refer to like parts throughout. f

F igure 1 is a diagrammatic representation of lamps A and B embodying myinvention connected in parallel to a common current source.

Figure 2 diagrannnatically indicates the connection of a plurality of mylamps in series, E, the series being itself in-parallel with a lamp Cand a lamp D.

conventional seriescircuit containing resistance, inductance, andcapacity.

' Figure 4: 1sa vector diagram for the circuit of Figure '3, assumingarbitrary values for the resistance, inductance and capacity. J

Flgure 5 is' a vector diagram for the circuit of Figure 3 under theconditions of series resonance. Figure 6 shows a lamp embodying myinvention in which the electron-emitting bodies 5 are heated by separatecurrent sources, and a voltage drop is maintained between them by seriesresonance in another circuit.

Thedevelopment of the audion tube has served to familiarize theart withthe phenomenon of electron emission from a hot body,

particularly when that body is connected to the negative side ofa directcurrent Source, and the positive line from the source is connected to'anelement maintained adjacent to the hot body and within the tube. Ipropose to apply this phenomenon to increase greatly the light-givingeffectiveness of an electric lamp.

I ope me at my lamp from an alternating curanother, because this wouldprevent the mainf rent source, and am thus able to employ a plurality ofhot bodies within the electric lamp. Considering for the present only a.single phase source, I will use two hot bodies within the lamp, oneconnected to each side of the current source, so that the direction ofelectron flow from or toward either body will reverse with the reversalsof the current.

It would of course be possible to maintain the temperature of the hotbodies by connection to current sources local to each of them, as isdone in the familiar A battery circuit of the audion tube. This would,however, be

complicated, expensive, and ineflicient, and therefore I prefer tomaintain the temper ature of the hot bodies by RP heating from the linecurrent. I do not pass the line current directly from one of the hotbodies to tenance of a high voltage drop between them,

such as is essential to the production of light" from electronbombardment.

7 While I intend to maintain a considerable voltage between the heatedbodies in the lamp, I plan to avoid distributing high voltage current ina building in which the lamp may be employed.

I find-that it is possible to secure a high voltage drop across theheated bodies within and E with the assumed current value I.

It is there seen-that the current lags the voltage E by the angle a, sothat the power factor regulation will be poor. I

If the circuit be resonated, however-that is, if the inductive reactanceand the capacitative reactance be made equalthe power factor willbecome. unity. Obviously, under this condition, the voltage drop Eacross the capacity will equal the voltage dropE across the inductance,and the line voltage will equal the voltage drop E across theresistance, merely. This is apparent from Figure 5.

Thus a very high voltage drop may be maintained across the inductance,although the line voltage is low.

With the ,usual line frequency, such as cycles for example, the size ofthe inductance coil or of the condenser required to maintain resonancewould be prohibitive from a commercial standpoint. However, at highfrequency, the circuit may be resonated by the use of very littleinductance for a given capacity. This may be understood by expressingthe frequency 7 under the conditions of resonance in terms of thecoeflicient of selfinduction L and the capacity C. For. resonance theinductive reactance X must equal the capacitative reactance X Now (Gray,Principles and Practice of Electrical Engineering, McGraw Hill Company.

(3d ed. 1924) 213, 227). During resonance For any given capacity, thesize of the inductance coil requiredto resonate the circuit is inverselyproportional to the square of the requency.

Thus byfar the greatest advantage from my invention is to be derived by0 eration on high frequency current preferab y at about 1000 cycles. Aconsiderable by-product advantage will be obtained because my lamps mayoperate from circuits designed for high frequency induction furnaceoperation or for other/uses.

Referring now to Figure 1, I there show a source of alternating current10 supplying current to lines 11 and 12 at any suitable voltage, forexample, at 220 volts. In lamp A,

the lamp body 13, constructed of glass or any other suitable transparentor translucent material, contains the hot electron-emitting bodies 14and 15, attached'to terminals 16,

17 ,1 18 and 19 extending through theglass wa l. v

The lines 19 and 20, extending from OPPO'.

site sides of the supply mains 11 and 12, are connected respectively. toone side of the reactances 21 and 22, here shown as condensers.

The other sides of the reactances 21 and 22 are connected to theterminals 16 and 18 re spectively. The terminals 17 .and 19 at the otherends of the filaments are attached to the respective ends of theopposite reactance 23. in this case an inductance coil.

'- .The bulb 13 may contain air highly evacuated. Or else, if desired,the air initially present in the bulb may be replaced by a suitable gas,which may be evacuated. As an alternative I may prefer to fill the bulbwith an inert gas such'as nitrogen, argon, etc., at normal atmosphericor low pressure. It is well known that the color of the light emitted,or, more strictly, the wave lengths of the most prominent radiationswithin the luminous range, depends .to a considerable extent upon thecharacter of the substance which is made to glow. I may vtherefore obtain lights of various colors and characteristics by proper choice ofthe gaseous atmosphere surrounding the electron-emitting odies.

to that which may be produced in gases. I

may cause the electron flow to impinge upon solid bodies adj acent'tothe electron-emitting bodies, more particularly the walls of the tube.By use of special glass, or of other similar substances, for my tubewall, I may produce fluorescence in the wall under the electronbombardment, and'employ this'as an additional light-giving means.

' As seen from the vector diagram of Figure a high alternating potentialdifference ex ists between thev filaments 14 and 15.

The

filaments are maintained at an incandescent temperature by currentflowing through them, and will produce light as in the case of anyincandescent lamp filament. In addition to this the electron flowalternately from one filament to the other will bombard the molecules ofenvironmental gas and cause them to produce light. And the bombardmentagainst the tube walls, or against any solid body exposed within thetube, may cause further luminescence.

The spacing of. the electron-emitting bodies, 'whether'close or farapart, as well as their shape, will depend upon the size of the lamp,the direction in which the light is to be directed, the voltage andfrequency at which the lamp is to operate, the disposition of thesupporting structure within the lamp, and the character of the gaseousatmosphere about the hot bodies, among other things. I therefore intendthe disposition of the filaments in lamp A'of Figure 1 to be purelydiagrammatic.. I of course do not wish to suggest that the distancebetween thefilaments would be the same as that shown when my inventionis embodied in an actual lamp of any size.

I intend to indicate that the electron-emitting body may be of any shapeor form, whether a rod, sheet, wire, plate or grid, or any othersuitable structure. In lamp I show thebodies disposed in the form ofgrids 1 L and 15', which may be pressed from sheet material, or bentfrom rod, tubing, or wire. In lamp C Ishow concentric-helical filaments1 F and 15 disposed one about the other to permit the inclusion ofconsiderable filament length within a small tube inclose proximity toanother filament similarly placed. Other arrangements of theelectronemitting bodies will doubtless suggest themselves to personsskilled in the art, and it is my intention to claim all such as mayembody my invention. a In Figure 6 I illustrate a form which I do'notconsider desirable, but which serves to make plain that myelectron-emitting bodies maybe maintained hot from separate thatpositive reactance (inductance 21 current sources, as 10 and 10 whilethe potential difference between them is due to'series resonance in acircuit consisting of the is opposite in character and proper in amountto produce series resonance. Thus in lamps A and B of Figure 1 and lampC of Figure 2, the reactance between the electron-emitting bodies ispositive (inductance 23) so that elsewhere in the circuit negativereactance (ca acity 21 and 22 or 21) must be provided. 11 the otherhand, in lamp D of Figure 2 the reactance between the electronemittingbodies is negative (capacity23 so and 22 must be supplied elsewhere.

Thus it will be evident that the reactance between the electron-emittingbodies may be either negative or positive, but that in any case oppositereactance must be placed elsewhere in the circuit to resonate it.

Provided reactance is included in the lamp circuit between theelectron-emitting bodies In lamp B I show only one condenser 21,connected in series between the current source and the source ofcurrent, it is immaterial 9 how it is disposed. In lamp A I show myvreactance in the 'form of two condensers 21 and 22, in series with thelamp between the current source and the respective filaments. Q

and one of the filaments. From an electrical standpoint either of theseforms is permissible, but I prefer the symmetrical disposition of thereactance as shown in lamp A and throughout Figure 2. The reactance maybe made up of several units, in series or in parallel, instead of. beinga single inductance or condenser.

In Figure 1 I show two of my lamps con nected in; parallel to the samesupply source.

In Figure 2 I show four lamps E connectedv invention according to theprinciples here disclosed, applying the well known circuits for currentsof any. given phase.

It will be evident that by using current at high frequency I obtain theadvantages of working under unity power factor, of obtaining greatereificiency and of distributing current much more-simply and cheaply thanwould be possible at low frequency. In addition, I obtain the furtheradvantages over the ordinary incandescent lamp that the size of my lampis not restricted by the convenient filament size, for the entire lampwill glow and serve as a source of light instead of merely a relativelysmall filament.

In manufacturing .my lamp it would doubtless be possible to construct.the inductance coil and the capacities as part of the lamp body or ofthe lamp mounting, but I do not propose to restrict my invention to anyspecific lamp structure. I rather desire to protect any structure whichinvolves the principles disclosed.

In view of my lnventlon and disclosure variations and modifications tomeet individual whim or particular need will doubtless. become evidentto others skilled in the art, to obtain part or all of the benefits ofmy invention without copying the structure shdwn, and I, therefore,claim all such in so far as they fall within the reasonable spirit andscope of my invention.

3. The method of electric lighting which consists in electricallyheating a plurality of elements within a lamp, maintaining a reactivepotential difference between the elements and producing series resonanpeof theheating current path.

4. The method of electric lighting which consists in maintaining aplurality of separate incandescent current'paths in seriesin a closedsystem containing a gas at-substantially different potentials of highfrequency by reactive voltage drop, across the current paths andproducing luminescence by cur rent discharge through said gas due to thepotential difl'erence between said current aths. j p 5. The method ofelectric lighting which consists in resonating a circuit including alurality of hot current paths, in maintain- 1n the hot current paths ina closed system at su stantially different potentials and in pro ducingluminescence from electron emission due to the potential difference.

6. In an electric lamp, a source of current supply, a lamp bodycontaining a plurality of elements adapted to be heated toincanrespective elements, reactance in the connections, and oppositereactance connected from one element to another.

7. Inan electric lamp, a source of current supply, a lamp bodycontaining a plurality of filaments each having two contacts,connections from the .source to one contact of each filament, reactancein one of the connections and connections, including opposite reactance,joining the other contacts of the filaments.

8. In an electric lamp, a source of current supply, a lamp bodycontaining a plurality of filaments each having two contacts,connections from the source to one contact of each filament, reactancein the connections.

connections from the further current source to one contact of eachfilament, reactance in the circuit, and opposite reactance between mgeach filament, a further current source,

.descence, connections from" the source to the y the other contacts ofthe filaments appro I priate to produce series resonance in the circultat the frequency of the further source.

10. In electric lighting, a source of ourrent supply, a lamp bodycontaining two I filaments, reactance connected between the filaments,connections from each filament. to the current source and oppositereactance between the lamp and the source.

11. In an'electric lighting system, a source of current supply, aplurality of lamps each containing aplurality of filaments, connectionsfrom the source to one end of each filament in one lamp iljicludingreactance between the source and the lamp, connections from the otherends of the filaments of that lamp to the respective ends of thefilaments of other lamps so as to place the filaments electrically inseries, and opposite reactance 'lbetween the ends of the filaments ofthe last amp. v

12. In electric lighting, a plurality. of

lamps each containing more than one filament, reactance connected at itsrespective ends to one end of each filament, a source of current supply,and connections, including opposite reactance, to the supply from theother end of each filament placing the lamps electrically in parallel.

13. The. method of producing light, which consists in setting up seriesresonance in a current path including reactance and in impressing thereactive voltage drop across the environmental gas in a closed system.

14. The method of producing li ht, using electrodes in a closed system,whic consists in heating the electrodes, in setting up series resonancein a current path including reactance and in impressing the reactivevoltage drop between the electrodes. I

15. The method of producing a. discharge across a tube from a source ata voltage too low to send current across the tube, which consists inproducin series resonance and in connecting the tube ietween points ofmaximum difference in displacement of voltage with respect to curren 16.The method of producing light, using a tube having elements, whichconsists in passing alternating current successively through areactance, to a hot-element of a tube, through an opposite reactance andto another element of the tube.

I 17. In ane1ectric circuit, a tube having elements, asource ofalternating current, circuit connections from the source to'the elementsand means for producing series resonance in the circuitand for producinga reactive otential drop between the elements.

18. 11 an electric circuit, a tube having elements, means for heating anelement, a source of alternating current, circuit connections from thesource to the elements and means 80 for producing series resonancein thecircuit and for producing a reactive potential drop between theelements.

' 19. An electric circuit including in series.

in the ordernamed, a source of alternating current at high frequency, areactance, an element of a tube, an opposite reactance and anotherelement of the tube.

EDWIN FITCH NORTHRUP.

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